Field of the Invention
This invention relates to combine harvesters of the conventional type and of the so-called rotary type such as an axial flow combine harvester.
As is well known, combine harvesters normally have a header with a cutter for cutting standing crop, the cut crop being conveyed by an elevator to a threshing mechanism comprising a concave through which threshed crop material falls to a grain pan. The straw issuing from the threshing mechanism passes to another device which assists in the further separation from the straw of any grain entrained in the latter, this crop material also being guided to the grain pan. The crop material received on the grain pan is transferred to a grain cleaning mechanism which comprises an upper chaffer sieve, a lower sieve and a fan operative to blow air through the two sieves from below so as to render airborne chaff and dust, for example, which is then discharged from the rear of the machine leaving the grain in a clean condition. The sieves are reciprocated and clean grain falls therethrough to a grain trough and from there is transferred to a grain tank. Any unthreshed crop (known as "tailings") mixed with the crop material on the sieves is too large to pass therethrough and is progressively moved rearwardly of the machine until it falls from the ends of the sieves to a tailings trough from where the tailings are conveyed to the threshing mechanism, or to a separate tailings thresher, for rethreshing.
Reference will be made throughout this specification to "grain", "straw" and "crop material" and it is to be understood that "grain" covers the seed or kernel, "straw" covers the discardable part of the particular crop being harvested, and "crop material" covers a mixture of grain, straw particles and chaff.